1. Field of the Invention
This invention is concerned with novel and useful antistatic biconstituent strands and textile products made at least in part from said strands.
2. Description of the Prior Art
It is well known that static electricity is generated and transferred as one walks on conventional carpet structures made from synthetic hydrophobic fibrous materials, as for example nylon fibers, acrylic fibers, polyester fibers and the like. When a person walking across such a surface later becomes grounded, a flow of accumulated electrons occurs through that part of the individual's body which by chance comes in contact with a ground. This discharge may occur by touching a door knob, metal cabinet, etc. When such electrical build-up exceeds 3500 volts, the electric shock is quite annoying to most people and can cause considerable personal discomfort. Many approaches have been suggested to eliminate or reduce the static electricity in fabrics in order to give much more comfort to the consumer and to reduce the danger of explosion where explosive materials may be present in the vicinity of fabric utilization.
It has been suggested to randomly intermingle a small amount of metal fibers or metal plated polymer fibers among synthetic hydrophobic fibers to reduce the static propensity of products made therefrom. This approach gives rise to considerable added cost and the resulting metallic glitter may be undesirable.
The use of fibers made of synthetic polymer having electrically conductive carbon black uniformly dispersed throughout has been suggested. However, such carbon-loaded filaments cannot be produced at economically high speeds at low cost. Moreover, the filaments tend to be brittle and thus are easily broken.
It has also been suggested to paste coat filaments with conductive substances or to soften the surface of a synthetic polymer filament and thereafter to cause electrically conductive carbon black to be deposited on and to adhere to the surface. Unfortunately, these approaches are expensive, slow speed operations; and obtaining uniformity of deposition is fraught with difficulties. In the aforementioned instances where carbon black is employed, the presence of the black filaments is quite noticeable in light colored textile goods because of a tell-tale gray appearance imparted thereto.
In U.S. Pat. No. 3,803,453 a sheath-core antistatic filament is described. The core component comprises preferably a minor amount of the filament and contains electrically conductive carbon black. In this way the blackness to a large extent is hidden, provided that the percent of core in the filament is less than 50. By completely encasing such a core component with a sheath of non-conductive polymer, one can realize only a very small part of the conductivity provided by the carbon black. While this known type of filament is somewhat effective in instances where the static buildup greatly exceeds 5000 volts, it has been found to be quite ineffective in reducing the static electricity below the 3500 volt level of normal human sensitivity.
It is also well known to produce a bicomponent filament of dissimilar materials by joining the same in a stratified flow of polymer melts through a spinnerette assembly without intimate mixing of the materials. Incorporating carbon black in a polymer drastically changes its flow behavior. Normally, when polymers having pronouncedly different flow behaviors are conjugated in a side-by-side arrangement to produce a bicomponent filament, there is an undesirable tendency for one component to fracture or to separate from the other so as to form a split filament.
There exists a real need in the field of man-made fibers to provide an electrically conductive strand of excellent pliability and flexibility that will permanently aid in the elimination of static electricity when intermingled even in minor amounts with static-prone fibers and yet that is relatively inexpensive to produce.